US 4362648 A
A catalyst composition can be obtained by gently milling a milled mixture of magnesium chloride and a titanium tetrahalide with a magnesium alkoxide. The catalyst composition can be combined with a metallic hydride or, preferably, an organometallic co-catalyst, e.g., an organoaluminum compound, to form a catalyst useful for the polymerization of alpha-olefins.
1. A catalyst composition obtained by gently milling a magnesium alkoxide with a milled mixture of a magnesium halide compound and a titanium tetrahalide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture.
2. A catalyst composition in accordance with claim 1 wherein the magnesium alkoxide is rotary ball milled with the milled mixture.
3. A catalyst composition in accordance with claim 1 wherein a powdered diluent is added to the composition.
4. A catalyst composition in accordance with claim 3 wherein said powdered diluent has a particle size of no greater than about 250 microns.
5. A catalyst composition in accordance with claim 3 wherein said powdered diluent is polyarylene sulfide.
6. A catalyst composition in accordance with claim 1 wherein the molar ratio of the magnesium halide to the titanium tetrahalide is in the range of about 2:1 to about 25:1 and the molar ratio of titanium tetrahalide to magnesium alkoxide is in the range of about 0.1:1 to about 10:1.
7. A catalyst composition in accordance with claim 5 wherein the molar ratio of the magnesium chloride to the titanium tetrahalide is in the range of about 3:1 to about 15:1 and the molar ratio of titanium tetrahalide to magnesium alkoxide is in the range of about 0.5:1 to about 5:1.
8. A method for preparing a catalyst composition comprising preparing a milled mixture of magnesium chloride and a titanium tetrachloride, and then gently milling the mixture with a magnesium alkoxide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture.
9. A method in accordance with claim 8 wherein said milled mixture is rotary ball milled with the magnesium alkoxide.
10. A method in accordance with claim 8 wherein the milling times are in the range of about 5 to about 200 hours.
11. A method in accordance with claim 10 wherein a powdered diluent is added to the composition subjected to said gently milling operation.
12. A method in accordance with claim 11 wherein said powdered diluent is added to the composition along with the magnesium alkoxide.
13. A method in accordance with claim 12 wherein the powdered diluent added to the compositions is poly(arylene sulfide).
14. A catalyst for the polymerization and copolymerization of olefins comprising two components A and B wherein:
component A is obtained by gently milling magnesium alkoxide with a milled mixture of a magnesium chloride and a titanium tetrahalide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture, and
component B is a metallic hydride or organometallic compound wherein said metal is selected from an element of Groups IA, IIA and IIIA of the Periodic Table.
15. A catalyst in accordance with claim 14 wherein the magnesium alkoxide is rotary ball milled with said milled mixture.
16. A catalyst composition in accordance with claim 14 wherein a powdered diluent is added to the composition subjected to said gently milling operation.
17. A catalyst in accordance with claim 16 wherein said powdered diluent has a particle size of no greater than about 250 microns.
18. A catalyst in accordance with claim 16 wherein said powdered diluent is poly(arylene sulfide).
19. A catalyst in accordance with claim 18 wherein said titanium tetrahalide is titanium tetrachloride.
20. A catalyst in accordance with claim 18 wherein component B is an organoaluminum compound.
21. A catalyst in accordance with claim 20 wherein the organoaluminum compound is selected from the group consisting of trimethylaluminum, triethylaluminum, tridodecylaluminum, tricyclohexylaluminum, triphenylaluminum, diethylaluminum chloride, diisobutylaluminum hydride and ethylaluminum dibromide.
22. A catalyst in accordance with claim 18 wherein the molar ratio of the magnesium chloride to the titanium tetrahalide is in the range of about 2:1 to about 25:1 and the molar ratio of titanium tetrahalide to magnesium alkoxide is in the range of about 0.1:1 to about 10:1.
23. A catalyst in accordance with claim 22 wherein the molar ratio of the magnesium chloride to the titanium tetrahalide is in the range of about 3:1 to about 15:1 and the molar ratio of titanium tetrahalide compound to magnesium alkoxide is in the range of about 0.5:1 to about 5:1.
24. A method for the preparation of a catalyst which comprises:
forming a component A by preparing an intimate mixture by milling a magnesium chloride and a titanium tetrahalide and then gently milling said mixture with a magnesium alkoxide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture, and then
combining component A with a component B which is a metallic hydride or organometallic compound wherein said metal is selected from an element of Groups IA, IIA and IIIA of the Periodic Table.
25. A method in accordance with claim 24 wherein the magnesium chloride and titanium tetrahalide mixture is rotary ball milled with the magnesium alkoxide.
26. A method in accordance with claim 24 wherein the milling times are in the range of about 5 to about 200 hours.
27. A method in accordance with claim 24 wherein powdered diluent is added to the composition.
28. A method in accordance with claim 27 wherein said powdered diluent is added to the composition along with the magnesium alkoxide.
29. A method in accordance with claim 27 wherein the powdered diluent added to the composition is poly(arylene sulfide).
30. A catalyst composition obtained by milling a magnesium alkoxide with a milled mixture of a magnesium halide compound and a titanium tetrahalide, said milling of magnesium alkoxide with said milled mixture being carried out by rotating a milling vessel at speeds ranging from about 10 to 200 rpm.
This application is a continuation-in-part of our co-pending application Ser. No. 003,439, filed Jan. 15, 1979 and now U.S. Pat. No. 4,240,929.
This invention relates to a process for polymerizing olefins. In another aspect, this invention relates to a catalyst composition for the polymerization of alpha-olefins. In another aspect, this invention relates to a process for preparing a catalyst which can be used in an alpha-olefin polymerization reaction. In another aspect, this invention relates to a catalyst composition which can be used in conjunction with a metallic hydride or organometallic co-catalyst to form a complete catalyst system useful in the polymerization of alpha-olefins. In yet another aspect, this invention relates to a catalyst composition to which a powdered diluent is added.
It is known to polymerize alpha-olefins and mixtures thereof according to the low pressure process of Ziegler. In this process, the catalysts used are prepared from mixtures of compounds of elements of Subgroups IV to VI of the Periodic Table and the organometallic compounds of the elements of Groups I to III of the Periodic Table. The polymerization is generally carried out in suspension, in solution or even in the gaseous phase.
Furthermore, processes using catalysts prepared by reacting a magnesium alkoxide compound with a compound of an element of Groups IV to VI of the Periodic Table are known. For example, according to U.S. Pat. No. 3,644,318, a compound of an element of Groups IV to VI of the Periodic Table, e.g., titanium tetrachloride, is reacted with a magnesium alkoxide to form a catalyst component. This catalyst component can then be mixed with an organoaluminum compound as co-catalyst.
The activity of an olefin polymerization catalyst is one important factor in a continuous search for the ultimate catalyst to be used in an alpha-olefin polymerization reaction. The higher the activity and productivity of the alpha-olefin polymerization catalyst, assuming the properties and qualities of the polymer product remain the same, the greater the favorability and acceptability of the catalyst for use in alpha-olefin polymerization reactions. Although catalysts that are prepared by reacting a magnesium alkoxide with a titanium compound have been found to be acceptable, improvements can be made.
It is an object of this invention, therefore, to provide an improved process for the polymerization of olefins.
Another object of this invention is to provide a novel and improved catalyst for the polymerization of alpha-olefins.
Another object of this invention is to increase the polymer production in an alpha-olefin polymerization process.
Still another object of this invention is to provide a catalyst of increased activity for the polymerization of alpha-olefins.
Other objects, aspects and the several advantages of this invention will become apparent to those skilled in the art upon the study of this disclosure and the appended claims.
The present invention provides a catalyst composition useful for the polymerization of alpha-olefins. The catalyst composition is obtained by mixing a magnesium alkoxide with an intimate mixture of a magnesium halide compound and a tetravalent, halogenated titanium compound. The catalyst composition is then combined with an organometallic co-catalyst to form a catalyst system useful in the polymerization of alpha-olefins.
In accordance with this invention a catalyst component for the polymerization of alphaolefins is obtained by gently milling magnesium alkoxide and a milled mixture of magnesium chloride and titanium tetrahalide. It has been found that a surprisingly high polymer productivity is obtained when the milled mixture of magnesium dichloride and titanium tetrahalide is only gently milled with magnesium alkoxide.
Throughout this application the term "gently milling" is intended to mean a milling operation wherein the milled mixture of magnesium chloride and titanium tetrahalide together with the magnesium alkoxide is placed into a receptacle together with grinding elements; the receptacle is subjected to a moderate movement to cause tumbling of these grinding elements. The movement can be a movement of rotating, rocking or gently shaking the receptacle. The movement of the receptacle is such that only up to about 300 of the shaking, rocking or rotating movements occur per minute. Thus, as an example the receptacle may be rotated at up to about 300 rpm, or specifically for instance at 150-200 rpm. The grinding elements utilized can vary in shape as well as in the material from which they are made; examples for such grinding elements include steel balls as well as zirconia cylinders.
One embodiment of this invention pertains to the formation of a catalyst composition wherein an intimate magnesium halide-titanium compound mixture is formed by milling and then milling the intimate mixture with a magnesium alkoxide. Many forms of milling can be used, however, it is preferred that the magnesium alkoxide is rotary ball milled with the intimate magnesium halide-titanium compound mixture as a highly active catalyst composition is thereby formed.
In another embodiment, the catalyst composition contains a powdered diluent. The powdered diluent added to the composition can be polymer fines of polymers such as polyethylene, polypropylene, poly(arylene sulfide) and the like or refractory substances such as alumina, silica, chlorinated silica and the like. It is preferred to add the powdered diluent to the catalyst composition when the magnesium alkoxide is added to the magnesium halide-titanium compound mixture in order to eliminate or reduce caking that can occur during the subsequent milling operation. The preferred powdered diluents are poly(arylene sulfide) and chlorinated silica.
In another embodiment of the invention, the catalyst composition is combined with an organometallic co-catalyst to form an active catalyst suitable for the polymerization of alpha-olefins such as ethylene. The organometallic co-catalyst can be selected from the organometallic compounds that form with the metals of Groups IA, IIA or IIIA of the Periodic Table, e.g., an organo-aluminum compound.
The catalyst composition of this invention is obtained by mixing a magnesium alkoxide with an intimate mixture of a magnesium halide compound and a tetravalent, halogenated titanium compound. The catalyst system, when used in combination with an organometallic compound, such as an organoaluminum compound, has been shown to be active for polymerizing olefins into normally solid polymers which can be fabricated into such useful articles as fibers, film, molded objects and the like.
The catalyst systems of this invention are especially active for the production of ethylene homopolymers or copolymers containing up to about 20 mole percent comonomer, the comonomer being selected from aliphatic 1-olefins containing from 3 to 10 carbon atoms per molecule. The catalyst system is useful in the polymerization of alpha-olefins, especially for the polymerization of alpha-olefins such as ethylene.
Any suitable magnesium alkoxide can be employed for the purpose of forming the catalyst composition of this invention as there is no restriction on the hydrocarbyl groups outside of practical considerations, e.g., ease of preparation and availability. Exemplary magnesium alkoxides can be expressed as Mg(OR)2 in which R is an alkyl group containing from 1 to 20 carbon atoms. Exemplary compounds include magnesium methoxide, magnesium ethoxide, magnesium isopropoxide, magnesium 2-ethylhexyloxide, magnesium dodecyloxide, magnesium eicosyloxide. Presently preferred compounds, because of ready availability and relatively low cost, are magnesium methoxide and magnesium ethoxide. The compounds can contain up to about 3 moles of the corresponding alcohol per mole of compound.
Any suitable tetravalent, halogenated titanium compound can be used as long as the titanium has one halogen attached thereto. Suitable compounds can be represented by the formula TiXa (OR')4-a in which X stands for bromine, chlorine or iodine or mixtures thereof, a is an integer of 1 to 4 and R' is an alkyl, cycloalkyl, or aryl group and combinations thereof, such as alkaryl, containing from 1 to about 20 carbon atoms. Specific examples of suitable compounds include titanium tetrachloride, titanium dibromodichloride, titanium iodotrichloride, n-butoxytrichlorotitanium, chlorotridodecyloxytitanium, bromotricyclohexyloxytitanium, diphenoxydichlorotitanium, and the like.
The most preferred tetravalent, halogenated titanium compounds are the titanium tetrahalides which include TiBr4, TiCl4, TiI4 and mixtures thereof. Presently preferred is TiCl4 because of ready availability and relatively low cost.
The magnesium halide compounds appropriate for the purposes of this invention are the magnesium dihalides with magnesium chloride being the preferred compound. Magnesium chloride is generally employed in the form of a finely divided powder. It can be preactivated by a grinding step although such preactivation is not considered generally necessary.
The molar ratio of the magnesium halide to the titanium compound can range rather widely as long as the final catalyst is effective for polymerization. However, a presently preferred molar ratio of magnesium halide to titanium compound is in the range of about 2:1 to 25:1 with the most preferred molar ratios being in the range of about 3:1 to 15:1 because catalyst activity is especially good in that range.
The molar ratio of titanium compound to magnesium alkoxide can range from about 0.1:1 to 10:1 and more preferably from about 0.5:1 to 5:1 since catalytic activity is especially high in that range.
The catalyst composition is prepared by first preparing an intimate mixture of the magnesium halide and tetravalent, halogenated titanium compound. The magnesium halide and titanium compound can be admixed in any convenient method that insures intimate dispersion of components. Preferably, admixing is performed under intensive milling conditions such as prevail in a ball mill, vibrating ball mill, tower mill and the like. A typical mill employable is a vibratory ball mill such as a Vibratom, manufactured by Siebtechnik GMBH.
The magnesium halide and titanium compound mixture is then mixed with the magnesium alkoxide in any convenient fashion. Rotary ball milling is the preferred method of treating the magnesium halide and titanium compound mixture with the magnesium alkoxide since less caking of the mixture occurs than in a vibratory mill. By rotary ball milling it is meant the conventional form of ball milling wherein a horizontal vessel partly filled with balls, small cylinders, etc., is rotated at speeds ranging from about 10-200 rpm.
Milling can be done in an inert, dry atmosphere such as nitrogen, argon and the like under subatmospheric, atmospheric or superatmospheric pressures. Cooling can be employed to avoid excessive temperatures being generated such as about 65° C. (150° F.), which can adversely affect catalyst performance. Milling times can range from about 5 to 200 hours. Vibratory milling typically requires a shorter time and rotary ball milling typically takes a longer time.
It is within the scope of the invention to dilute the catalyst compositions with a powdered diluent. Said diluent can be polymer fines, e.g., polyethylene, polypropylene, poly(arylene sulfide) and the like or refractory substances such as alumina, silica, chlorinated silica and the like. The preferred powdered diluents are poly(arylene sulfide) and chlorinated silica. The powdered diluent is preferably added along with the magnesium alkoxide to eliminate or reduce caking that can occur during the subsequent milling operation. When catalyst dilution is employed, a rotary ball mill or vibratory mill can be used to produce the final catalyst compositions. Such diluents have particle sizes ranging from about 60 mesh to 400 mesh (250-37 microns) or finer.
The amount of diluent employed with the catalyst can vary rather widely so long as a composite active for polymerization is obtained. Generally, the composite can contain from about 1 to 90 wt. % diluent.
The catalyst composition, component A, can then be combined with a co-catalyst, component B, to form a catalyst system useful for the polymerization of olefins. Component B is a hydride or organometallic compound wherein said metal is selected from an element of Groups IA, IIA and IIIA of the Periodic Table. In other words, component B can be a hydride of a metal selected from Group IA, IIA and IIIA or an organo-compound of the metals. The preferred compound to be used as component B is an organoaluminum compound which can be expressed as R"b AlX3-b in which R" is a hydrocarbon radical selected from such groups as alkyl, cycloalkyl, aryl, alkaryl, aralkyl, alkenyl and the like containing from 1 to 20 carbon atoms per molecule, X is halogen or hydrogen and b is an integer of 1, 2 or 3. Exemplary compounds include trimethylaluminum, triethylaluminum, dimethylaluminum chloride, n-propylaluminum diiodide, diisobutylaluminum hydride, didodecylaluminum bromide, trieicosyaluminum, tridodecylaluminum, tricyclohexylaluminum, triphenylaluminum, diethylaluminum chloride, ethylaluminum dibromide and the like and mixtures thereof.
Any mono-1-olefin can be polymerized in the presence of the catalyst of the present invention with the preferred reactant being ethylene or ethylene plus another higher aliphatic mono-1-olefin containing from 3-10 carbon atoms. The mono-1-olefin, or mixture thereof, is polymerized by contacting the catalyst system of this invention using any of the well known methods, e.g., by contacting in solution, in suspension or in gaseous phase, at temperatures ranging from about 20°-200° C. and pressures ranging from about atmospheric to about 1000 psig (6.9 MPa g). The homopolymerization and copolymerization reactions can be conducted batchwise or in continuous fashion by employing any known process.
It is convenient when polymerizing ethylene in a bench scale process, for example, to conduct the polymerization batchwise in a stirred reactor employing a dry hydrocarbon diluent inert in the process such as isobutane, n-heptane, methylcyclohexane, benzene, toluene and the like, at a reactor temperature of about 80° C. and a reactor pressure of about 280 psig (1.9 MPa). Ethylene is admitted to the reactor as required to maintain the desired pressure. Molecular weight control agents such as hydrogen can be employed in the reactor, as known in the art, to adjust the molecular weight of the polymer.
When the selected polymerization time is reached the reaction can be terminated by discontinuing the flow of ethylene and comonomer, if used, venting unreacted monomer(s) and diluent and recovering the polymer. The recovered product can be treated to deactivate or remove catalyst residues such as by an alcohol wash, can be stabilized by admixture with an antioxidant(s) and can be dried to remove residual solvent, if present, as is known in the art. Generally, because such low amounts of catalyst residues are present in the polymer product it is not necessary to remove them to avoid discoloration of the polymer or corrosion of processing equipment. Thus, it is usually only necessary to stabilize the polymer after recovery and dry it before it is further processed into pellets and/or converted into the final shaped product.
The present invention will be better understood upon study of the following examples. The following examples are set forth as illustrative of this invention and are not meant to be restrictive in any way.
A series of magnesium dichloride-titanium tetrachloride mixtures was prepared by individually charging a 1 liter spherical steel vessel under nitrogen with 100 g of the mixture and 2400 g of 3/8 inch (0.95 cm) steel balls. Vibratory ball milling was employed at ambient conditions for a period of time ranging from 16-24 hours. Each sample was recovered through a restricted passage in the vessel opening which allowed passage only of the milled product. Each sample was stored under nitrogen in a dry box until further use. The mole ratio of MgCl2 -TiCl4 ranged from 4.7:1 to 10.5:1 in the samples thus prepared.
Samples of the MgCl2 -TiCl4 mixtures of 10 g or 20 g were subsequently rotary ball milled with suitable quantities of the magnesium alkoxide and diluent, if employed, by charging the components in a nitrogen atmosphere to a 0.24 liter ceramic vessel containing from 300-400 g of cylindrical zirconia grinding media of 1/2×1/2 inches (1.3×1.3 cm) dimensions. Each sample was mixed by rotating at ambient temperature for 24 hours at about 140 RPM. The products were recovered by passage through an 8 mesh screen and stored in a dry box under nitrogen until ready for testing as ethylene polymerization catalysts. The exact mole ratios and/or weight ratios of the components employed are detailed in subsequent examples.
A 3.8 liter, stirred, stainless steel reactor was employed for ethylene polymerization. The reactor was readied for each run by charging 3 liters of dry n-heptane to it, closing the port, and heating reactor and contents at 175° C. for 30 minutes. The reactor was drained and residual heptane purged with dry nitrogen. The reactor was then closed and cooled under nitrogen pressure.
The prepared reactor was purged with dry isobutane vapor and 3 ml of the co-catalyst solution of 15 wt % triethylaluminum in dry n-heptane (2.8 mmoles) was added followed by the catalyst. The reactor was closed, 2 liters of dry isobutane charged, the reactor and contents were heated to 80° C. and 100 psi (0.69 MPa) ethylene pressure added.
After a one hour polymerization run, the reaction was terminated by flashing the ethylene and isobutane from the reactor. The polymer was then recovered and weighed to obtain the yield.
Each polymer yield was divided by the weight of catalyst employed to determine the calculated productivity expressed as kg polyethylene per g catalyst per hour. When the catalyst contains a diluent, the calculated productivity is based on kg polymer per g diluted catalyst as well as kg polymer per g catalyst contained in the diluted catalyst.
The quantities of catalyst components employed, mole ratios used and results obtained are presented in Table I.
TABLE I__________________________________________________________________________ETHYLENE POLYMERIZATION WITH MgCl4.Mg(OCH3)2 CATALYSTSCATALYST Calculated Cal- CALCULATED Productivities culated MOLE RATIOS Polymer kg polymer/gRun Weight mmoles Wt % MgCl2 TiCl4 Al Yield catalyst/hrNo. mg Ti Ti TiCl4 Mg(OR)2 Ti g Initial.sup.(a) Final__________________________________________________________________________1 11.3 0.018 7.6 4.3 2.9 155 416 10.2 36.82 5.7 0.0087 7.3 " 1.4 322 235 " 41.23 9.4 0.013 6.7 : 0.72 215 202 " 21.54 10.6 0.014 6.3 5.8 4.7 200 373 14.2 35.25 15.9 0.021 6.2 " 2.3 133 596 " 37.56 7.7 0.0098 6.1 " 1.6 286 409 " 68.37 2.9 0.0037 " " " 730 198 " 68.38 16.0.sup.(b) 0.0034 6.1.sup.(c) " " 823 202 " 12.6.sup.(d)9 8.0 0.0099 5.9 " 1.2 283 362 " 45.210 9.9 0.012 7.6 " " 233 434 " 43.811 2.0 0.0032 7.3 10.5 2.0 875 78 19.0 39.012 4.5 0.0069 6.7 " 1.6 406 203 " 45.113 3.3 0.0046 " 1.2 609 185 " 56.1__________________________________________________________________________ Notes:- .sup.(a) Before admixing Mg(OR)2 with MgCl2.Ticl4 catalyst .sup.(b) Catalyst weight excluding polyethylene diluent is 2.7 mg. calculated. .sup.(c) Based only on catalytic component. .sup.(d) Based on catalyst only (excluding diluent), catalyst productivit is calculated to be 74.8 kg polymer per g catalyst. Diluent is polyethylene fines dried under nitrogen at 80° C. for 24 hours. Particle size is less than 60 mesh (250 microns or less).
TABLE II__________________________________________________________________________EFFECT OF ALKOXIDE ON CATALYST COMPOSITIONCATALYST CALCULATED CALCULATED MOLE RATIOS Diluent Polymer CALCULATED PRODUCTIVITIESRun Total Free wt. % mmoles wt % MgCl2 TiCl4 Al Yield kg polymer/g catalyst/hrNo. mg mg cat. Ti Ti TiCl4 Mg(OR)2 Ti g Initial.sup.(e) Undiluted Diluted.sup.(f)__________________________________________________________________________14.sup.(a) 13.3 13.3 100 0.017 6.0 5.8 2.0 165 487 16 36.6 --15.sup.(a) 17.8 3.6 20 0.0045 " " " 622 184 " 51.1 10.316.sup.(a) 10.2 10.2 100 0.013 6.1 " 2.7 215 372 " 36.5 --17.sup.(a) 24.7 4.9 20 0.0062 " " " 452 228 " 46.5 9.218.sup.(a) 12.0 2.4 20 0.0030 6.2 " 3.3 933 132 " 55.0 11.019.sup.(a) 9.3 1.9 20 0.0025 6.3 " 4.0 1120 89 " 46.8 9.620.sup.(b) 9.1 9.1 100 0.012 6.1 " 2.0 233 224 " 24.6 --21.sup.(b) 12.9 12.9 " 0.017 6.3 " 3.3 165 282 " 21.9 --22.sup.(b) 11.5 11.5 " 0.015 6.3 " 4.0 187 313 " 27.2 --23.sup.(c) 5.7 5.7 " 0.0076 6.4 5.2 2.0 368 214 13 37.5 --24.sup.(d) 8.0 8.0 " 0.0099 5.9 5.8 1.2 283 362 14 45.2 --25.sup.(d) 4.9 4.9 " 0.012 " " " 233 434 " 43.8 --__________________________________________________________________________ Notes:- .sup.(a) Mg(OR)2 is Mg(OC2 H5)2, commercial sample. .sup.(b) Mg(OR)2 is Mg(OCH3)2, commercial sample. .sup.(c) Mg(OR)2 is Mg(OCH3)2.(CH3 OH)1.7, experimental preparation. .sup.(d) Mg(OR)2 is Mg(OCH3)2, experimental preparation. .sup.(e) Before admixing (Mg(OR)2 with MgCl2.TiCl4 catalyst. .sup.(f) Polyethylene fines, see footnote d, Table I, for description.
TABLE III__________________________________________________________________________EFFECT OF DILUENTS ON CATALYST ACTIVITY CATALYST CALCULATED CALCULATED MOLE RATIOS CALCULATED To- Diluent Polymer PRODUCTIVITIESRun tal Free wt % mmoles wt % MgCl2 TiCl4 Al Yield kg polymer/g catalyst/hrNo. Diluent mg mg cat. Ti Ti TiCl4 Mg(OR)2 Ti g Initial.sup.(e) Undiluted Diluted__________________________________________________________________________26 PPS.sup.(a) 10.9 3.8 34.6 0.0048 6.1 5.8 2.0 583 317 16.1 83.4 29.027 " 4.6 1.5 " 0.0019 " " " 1470 381 " 254..sup.(b) 82.828 " 3.8 1.3 34.2 0.0017 6.3 " 2.9 1650 144 " 73.1 25.029 " 3.9 1.3 34.0 0.0017 " " 3.9 " 141 " 108. 36.230 " 2.6 0.9 " 0.0012 " " " 2330 128 " 142. 49.231 " 9.1 3.1 " 0.0041 " " 683 277 " 89.4 30.432 Cl--Sio2.sup.(c) 10.1 3.4 34.2 0.0045 " " 2.9 622 255 " 75.0 25.233 " 3.6 1.2 34.7 0.0016 " " 3.8 1750 124 " 103. 34.434 " 3.0 1.0 " 0.0013 6.1 " 2.9 2150 104 " 104. 34.735 " 4.2 1.4 34.4 0.0018 6.2 " 3.9 1550 154 " 110. 36.736 SiO2.sup.(d) 10.2 6.6 34.2 0.0087 6.3 " 2.9 322 285 " 43.2 14.837 " 14.6 5.1 34.7 0.0065 6.1 " " 431 188 " 36.9 12.9__________________________________________________________________________ .sup.(a) Polyphenylene sulfide, U.S. Pat. No. 3,354,129. Unscreened, particle range from about 20 to less than 325 mesh (840 to less than 40 microns), about 74 wt % are 40-80 mesh. Dried under nitrogen for 24 hours at 80° C. .sup.(b) Three hour polymerization run. .sup.(c) Chlorinated microspheroidal silica, dried in chlorine ambient at 400° C. for 30 minutes. Particle sizes ranged from about 60 to les than 325 mesh (250 to less than 40 microns), about 61 wt % ranges from about 80-200 mesh. Material used unscreened. .sup.(d) Silicatitantia cogel containing about 2.5 wt % Ti, calcined in air at 870° C. and cooled to ambient temperature under dry nitrogen. Particle size distribution similar to silica of footnote .sup.(c). Material used unscreened. .sup.(e) Before admixing Mg(OR)2 with MgCl2.TiCl4 catalyst
The results in Table I show that MgCl2 TiCl4 catalysts of various mole ratios are significantly improved in ethylene polymerization activity by the addition of magnesium methoxide as described in this invention. Improvement is noted over the entire MgCl2 to TiCl4 mole ratio range of 4.3:1 to 10.5 to 1, and a ratio of 5.8:1 appears to be especially desirable. Run 8 results show that dilution of an invention catalyst with finely divided polyethylene also increases its activity even more.
Based on calculated productivity data obtained, the results show the invention catalyst containing no diluents are capable of producing polyethylene from about 1.1 to 4.8 times the quantities produced by the control catalysts containing no added magnesium methoxide.
The results presented in Table II in runs 14-19 show that magnesium ethoxide can be substituted for the methoxide to give catalyst composites quite active in ethylene polymerization. Run 24 demonstrates that magnesium methoxide containing 1.7 moles methanol per mole alkoxide is about as effective as the alcohol-free alkoxide in preparing the invention catalysts.
The enhanced activity imparted the invention catalysts by dilution with polyethylene fines is directly brought out in the results shown in runs 14 and 15 and in runs 16 and 17. Without a diluent calculated catalyst productivity is about 36.5 kg polymer per g catalyst. With a diluent calculated catalyst activity based on the Mg(OR)2 -promoted MgCl2.TiCl4 contained in the diluted catalyst reaches about 51 kg polymer per g catalyst in run 15 and 46.5 kg polymer per g catalyst in run 17.
The results shown in Table III demonstrate the effectiveness of several types of diluent for use with the invention catalysts. Particularly good results are shown with polyphenylene sulfide and chlorinated microspheroidal silica, e.g., calculated productivities ranging from 75-142 kg polymer per g catalyst. A silica-titania cogel is shown to be less effective than the chlorinated silica, possibly because the surface hydroxyl groups affect catalyst activity and do not permit the enhanced activity to develop as with the other diluents.
A series of catalysts was prepared to compare those made according to this invention with those prepared in other ways or outside the scope of this invention. For convenience the catalysts are described as follows:
A. Invention catalysts: These are described in Example 1 with the polymerization results given in Table 1, runs 6, 7, 8. The catalysts are made by vibratory ball milling MgCl2 -TiCl4 to obtain a composite which is subsequently rotary ball milled with Mg(OR)2 to produce the catalyst.
B. Invention catalysts prepared in an alternate but less preferable manner by vibratory ball milling the Mg(OR)2 with a vibratory ball milled MgCl2 -TiCl4 composite: Each catalyst sample was prepared by vibratory ball milling the specified quantity of Mg(OR)2 with the specified quantities of other components in a 1 liter, spherical stainless steel vessel containing about 2400 g of 0.95 cm diameter steel balls for 16 hours. The products were recovered as previously described. The amounts of components used are given in Table B.
TABLE B__________________________________________________________________________ Mole RatioRun Grams Components Mg(OCH3)2. TiCl4No. MgCl2.TiCl4.sup.(a) Diluent.sup.(b) Mg(OCH3)2 (MeOH)1.7 Mg(OR)2__________________________________________________________________________B1 45 45 2.6 0 2.0B2 45 45 2.2 0 2.4B3 45 45 1.9 0 2.8B4 80 0 0 7.6 2.0B5 80 0 0 6.3 2.4__________________________________________________________________________ .sup.(a) MgCl2 /TiCl4 mole ratio is 5.8:1 .sup.(b) See footnote .sup.(d) of Table III.
C. Control catalysts prepared from vibratory ball milling of MgCl2 with TiCl4 : The specified quantities of each component were charged to a 1 liter, spherical steel vessel containing about 2400 g of steel balls and milled the specified time on a vibratory mill. The products were recovered as previously described. The amounts of components used, size balls employed and milling times are listed in Table C.
TABLE C______________________________________Run Ball Size Milling Time Grams Mole RatioNo. cm hrs MgCl2 TiCl4 MgCl2 /TiCl4______________________________________C1 1.3 40 90.0 12.1 14.8:1C2 1.3 16 84.0 15.5 10.7:1C3 0.95 24 84.1 15.9 10.5:1C4 0.95 48 84.1 15.9 10.5:1______________________________________
D. Control catalysts prepared from Mg(OR)2 and TiCl4 by contacting a hydrocarbon-Mg(OR)2 slurry with TiCl4 :
Control catalyst D1 was prepared by refluxing 5 g of Mg(OCH3)2 (MeOH)0.5, slurried in about 150 ml of dry n-hexane contained in a 500 ml flask, with 51.8 g of TiCl4 for 4 hours (about 65° C.) while stirring. Stirring was discontinued, the mixture was cooled to room temperature, liquid decanted and the slurry was washed 3 times with 475 ml portions of fresh n-hexane. The product was dried at room temperature in a vacuum oven. The calculated molar ratio of TiCl4 to Mg(OCH3)2 is 5.5:1. (The actual amount of TiCl4 retained was not determined.)
Control catalyst D2 was prepared by reacting a ball milled Mg.MgCl2 composite (containing 2 g Mg) with 7.9 g methyl alcohol (1.5×stoichiometric) in the presence of about 200 ml dry n-hexane at reflux for 1 hour. The mixture was refluxed an additional 4 hours while stirring and then cooled to room temperature. Then to the stirred mixture was added 86.3 g of TiCl4 and about 100 ml of n-hexane and the mixture was refluxed for 4 hours, the stirring discontinued and the mixture was cooled to room temperature. The liquid was decanted and the product was washed 5 times with 450 ml portions of n-hexane. The washed product was dried at room temperature in a vacuum oven. The calculated molar ratio of TiCl4 to Mg(OCH3)2 is 5.4:1. (Actual TiCl4 retained not determined.)
The catalysts were subsequently employed in the polymerization of ethylene in the manner described in Example 2. The details and results obtained are presented in Table D.
TABLE D__________________________________________________________________________Catalyst Calculated Diluent Calculated Mole Ratios PolymerCatalystTotal Free mmoles Wt. % MgCl2 TiCl4 Al Yield Calculated ProductivitiesNo. mg mg Ti Ti TiCl4 Mg(OR)2 Ti g kg polymer/g Remarkst/hr__________________________________________________________________________A1 7.7 7.7 0.0098 6.1 5.8 1.6 286 409 53.1 inventionA2 2.9 2.9 0.0037 6.1 5.8 1.6 730 198 68.3 "A3 16.0.sup.(a) 2.7 0.0034 6.1.sup.(b) 5.8 1.6 823 202 74.8.sup.(c) "B1 13.8.sup.(g) 7.1 0.0023 3.2 5.8 2.0 1220 197 27.7.sup.(d) "B2 9.3.sup.(g) 4.8 0.0016 3.2 5.8 2.4 1750 118 24.6.sup.(e) "B3 16.5.sup.(g) 8.4 0.0028 3.2 5.8 2.8 1000 251 29.9.sup.(f) "B4 3.9 3.9 0.0012 5.9 5.8 2.0 2330 202 51.8 "B5 5.6 5.6 0.0018 6.0 5.8 2.4 1560 190 33.9 "C1 16.3 16.3 0.0102 3.0 14.8 na 275 349 21.4 controlC2 10.9 10.9 0.0090 3.9 10.7 na 311 216 19.8 "C3 14.8 14.8 0.0124 4.0 10.5 na 226 340 22.9 "C4 20.2 20.2 0.0169 4.0 10.5 na 166 440 21.8 "D1 14.6 14.6 nd nd nd nd nd 272 18.6 "D2 23.5 23.5 nd nd nd nd nd 252 10.7 "__________________________________________________________________________ Notes:- Results for catalysts A1, A2, A3 are repeated from Table I, runs 6,7,8, respectively. na means not applicable nd means not determined .sup.(a) Includes polyethylene diluent, see footnote .sup.(d) of Table .sup.(b) Based only on catalytic .sup.(c) Calculated productivity is 12.6 kg polymer per g catalyst plus diluent .sup.(d) Calculated productivity is 14.3 kg polymer per g catalyst plus diluent .sup.(e) Calculated productivity is 12.7 kg polymer per g catalyst .sup.(f) Calculated productivity is 15.2 kg polymer per g catalyst .sup.(g) Includes silica diluent, see footnote .sup.(d) of Table III, als Table B
Inspection of the data presented in Table D reveals that catalysts made according to the preferred mode of preparation (catalysts A1, A2, A3) exhibit good activity in polymerizing ethylene. That is, the best results are obtained when an MgCl2.TiCl4 composite is prepared by vibratory ball milling and that composite is subsequently admixed with Mg(OR)2 by employing rotary ball milling.
An alternate but less preferred method of producing the catalysts is shown by the B catalysts where the MgCl2.TiCl4 composite is subsequently admixed with Mg(OR)2 by employing vibratory ball milling. This system of mixing components appears to give erratic results which can be as good as the preferred process, e.g., polymerization results with A1 catalyst and B4 catalyst are similar but with B5 an unexpected drop in productivity occurs. However, the results with B5 catalyst are still substantially better than those obtained with control catalysts C1-C4 and D1, D2.
The substantially poorer polymerization results obtained with the C control catalysts consisting of MgCl2 and TiCl4 compared to the invention catalysts containing Mg(OR)2 points out the unexpected beneficial nature of the combination including MgCl2 and Mg(OR)2. This aspect is also shown in Table 1 where initial and final calculated productivities for the catalysts are disclosed.
The relatively poor polymerization results obtained with the D1 catalyst consisting only of Mg(OR)2 and TiCl4 indicates again that superior catalysts are made only when TiCl4, MgCl2 and Mg(OR)2 are combined. (The D catalysts were not analyzed, hence the amount of TiCl4 present in combination with Mg(OR)2 is unknown.) Furthermore, the results obtained with the D2 catalysts show that the specific manner of combining the titanium compound, magnesium halide and magnesium alkoxide can make a significant difference in catalyst activity.
In the following example, comparative runs were carried out to determine the effect of the nature of the milling utilized in the preparation of the first catalyst component.
The vibratory ball milling was carried out in a 225 mL vessel using the quantities of reagents shown in the following table. The vibratory ball milling was carried out in the presence of 14 stainless steel balls having a diameter of 13 mm.
The rotary milling in the second step of the present invention was carried out in a 240 mL vessel with 16 cyclindric zirconia rods having a diameter of 13 mm and a length of 13 mm.
The total milling time in all instances was 16 hours. In the case of runs 1, 2 and 4, the runs where the milling was carried out in two steps, the first step was a four-hour milling whereas the second step was a twelve-hour milling.
The catalyst component obtained in the four runs was used for polymerizing ethylene, employing 3 cc of a solution of 15% triethylaluminum in heptane as the cocatalyst. The polymerization was carried out at 80° C. for one hour with a partial pressure of ethylene of 100 psi (0.69 MPa). For further details, reference is made to example 2 of this patent application. The other quantities utilized in the preparation of the catalyst as well as the productivity of polyethylene are shown in the following table. In run 1, the milled mixture of magnesium chloride and titanium tetrachloride was removed from the milling vessel and charged to a porcelain vessel. Not the total quantity of 6.76 grams but only 5.47 grams of the complex was recovered and therefore the quantity of magnesium ethoxide utilized was smaller in run 1 as well. Since the weight ratio of the complex and the magnesium alkoxide utilized was, however, the same in all four runs and since the productivity is related to one gram of catalyst the results of these runs are fully comparable.
TABLE IV__________________________________________________________________________ (a) (b) (c) (d)__________________________________________________________________________ MgCl2 TiCl4Run MgCl2 TiCl4 Complex Mg(OEt)2 ProductivityNo. (g) (g) (g) (g) Procedure g/gcat/hr__________________________________________________________________________1 5.5 1.26 5.47 0.98 (1)vib. ball mill (a) + (b) → (c) (4 hr) 14,928 (2)then gently mill (c) + (d) (12 hr)2 5.5 1.26 6.76 1.21 (1)vib. ball mill (a) + (b) → (c) (4 hr) 4,100 (2)add (d), continue vib. ball milling (12 hr)3 5.5 1.26 6.76 1.21 (1)vib. ball mill 5,000 (a), (b), (d) (16 hr)4 5.5 1.26 6.76 1.21 (1)vib. ball mill 9,008 (a) + (d) → (e) (4 hr) add (b), continue vib. ball milling (12 hr)__________________________________________________________________________
The above results show that the process of this invention involving a gentle milling of a milled mixture of magnesium chloride and titanium tetrahalide with magnesium alkoxide (run 1) results in a surprisingly increased productivity compared with both processes in which the second milling step is a vibratory ball milling step (run 2) and processes in which the three ingredients are vibratory ball milled together in a one step milling operation (run 3). Furthermore, the inventive process also results in a far superior productivity than achieved by first vibratory ball milling magnesium chloride and magnesium ethoxide and then vibratory ball milling the so-obtained mixture with titanium tetrachloride (run 4).
Reasonable variations and modifications which will become apparent to those skilled in the art can be made in the present invention without departing from the spirit and scope thereof.
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